Abstract : Abstract: During July, August and September of 1993 and 1994, we successfully employed time-depth recorders, VHF transmitters and satellite-linked transmitters in a study of the diving behavior and habitat utilization of harbor porpoises in the Gulf of Maine and Bay of Fundy. A total of 190.4 hours of diving behavior (6002 dives) was recorded by time-depth recorders placed on four porpoises. Mean dive depths were between 22 + 23 and 41 + 32 m. The deepest recorded dive was 226 m, the maximum depth of the study area. Satellite tags were placed on three porpoises and transmitted location data for between 2 and 21 days. The satellite telemetry data shows that porpoises are highly mobile. One animal covered most of the known summer range of the Gulf of Maine harbor porpoise population in six days. Blood chemistry values were measured for 31 porpoises. Plasma cortisol and Creatinine levels were significantly higher (p=O.O356 and 0.0174, respectively) for animals that received electronic tags than for those that only received roto-tags.